Dating rock com
Most directly measure the amount of isotopes in rocks, using a mass spectrometer.
Others measure the subatomic particles that are emitted as an isotope decays.
Another example is luminescence dating, which measures the energy from radioactive decay that is trapped inside nearby crystals.
Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms." When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.So in order to date most older fossils, scientists look for layers of igneous rock or volcanic ash above and below the fossil.Scientists date igneous rock using elements that are slow to decay, such as uranium and potassium.Each isotope is identified with what is called a ‘mass number’.When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.